Cumulene-resin binder photoconductive elements

ABSTRACT

A photoelectrostatic member in a process for electrostatic imaging includes a photoconductive layer containing a compound selected from the general class of cumulenes dispersed in a resin binder applied to the member. The cumulene compounds useful in the instant invention have of the following general formulas:

United States Patent [1 1 Blanchette CUMULENE-RESIN BINDER PHOTOCONDUCTIVE ELEMENTS [75] Inventor: Robert G. Blanchette, Mayfield Heights, Ohio V [73] Assignee: Addressograph-Multigraph Corporation, Cleveland, Ohio 22 Filed: Mar. 26, 1973 21 Appl. No.: 345,104

Related US. Application Data [60] Continuation of Ser. No. 244,993, April l7, l972, abandoned, which is a division of Ser. No 78,628, Oct. 6, l970, Pat. No. 3,674,473, which. is a continuation-in-part of Ser. No. 771,352, Oct. 28, I968, abandoned.

Primary ExaminerRoland E. Martin, Jr. Attorney, Agent, or FirmSol L. Goldstein; Michael A. Kondzella Oct. 15, 1974 [5 7] I ABSTRACT A photoelectrostatic member in a process for electrostatic imaging includes a photoconductive layer containing a compound selected from the general class of cumulenes dispersed in a resin binder applied to the member. The cumulene compounds useful in the instant invention have of the following general for mulas;

where X represents an alkyl, hydrogen, halogen or nitro substituent; Q and 0 can be:

indene or fluorene;

n can be an integer from l through 6;

R is lower alkyl, aryl or hydrogen; R and R can be aryl, substituted aryl,

heterocyclic ring structures; and where 0,, Q or R and R can be the same or different.

6 Claims, No Drawings CUMULENE-RESIN BINDER PHOTOCONDUCTIVE ELEMENTS CROSS REFERENCE BACKGROUND OF THE INVENTION This invention relates to organic photoconductive materials and, more particularly, to a class of compounds known as cumulenes which contain a unit of m carbon atoms with (m 1) double bonds between them, where m is an integer equal to or greater than 3.

Photoelectrostatic imaging processes involve the use of a photoconductive medium which is charged in the dark, exposed to a pattern of light and shadow thereby producing a charge pattern corresponding to the image portions of the original design to be reproduced. This charge pattern is then developed by applying an electrostatically attractable powder generally known as toner in hwarts...

I SUMMARY OF THE INVENTION In accordance with the present invention a new class or organic photoeonductors is provided having any one of the following general formulas:

Q1(= )n=Q1 R J(=C)n=Qz R where X represents an alkyl, hydrogen, halogen or nitro substituent; Q, and O can be:

C Rz indene, or fluorene;

n can be an integer from I through 6; R is a lower alkyl, aryl or hydrogen; R and R can be aryl, substituted aryl, heterocyclic ring structures, fused arenic ring structures; and Q Q or R and R can be the same or different, said compound being dispersed in a resin binder.

The support on which the photoconductive material is applied may be paper which has been treated to render it conductive or it can be metal or metal foil such as aluminum, copper, or zinc. Generally, it is understood in this art that the basesupport must have a conductivity in the range from l0 mhos per centimeter to the conductivity of metal.

It is the general object of the present invention to provide an improved organic photoconductive medium formulated with compounds which contain a unit of (m) carbon atoms with (m l double bonds between them where (m) is an integer equal to or greater than It is another object of this invention to provide a photoconductive material comprised of organic crystalline materials selected from the general class of cumulenes.

It is still another object of this invention to provide a photoconductive member formulated with an organic crystalline material dispersed in an insulating resin binder which formulation is simple to prepare and which photoconductive member gives an increased photo response.

DESCRIPTION OF THE INVENTION:

Compounds which are typical of the cumulene-type materials useful in the preparation of the photoconductive members of this invention are the following:

List of compounds formula Name Bifiuoren ylidene-ethylene.

'Ietraphenyl-hexapentaene.

Tetraphenyl-butatriene.

List of compounds formula C) 0 Q o=o=o=o CH3 H 5; 1 o=o=o= 16 CH3 c113 mc o=o=c=o om 17 H36 CH3 H C- a z :0

1s CH3 CH3 tContinued Name 1,4-rli-2-imphthyl-l,4-(liph0nylbutalricne.

1,4-di(2,4-dimethylpheny1)4,4-

diphenylbutatriene.

1,4-dl(2,5-dimethy1phenyl)4,4-

diphenylbutatriene.

1 ,4-di (3,4-dimethylpheny1) -1 ,4-

diphenylbutatriene.

1,4-di(Z-methylbhenyD-IA- diphenylbutatriene.

1,4-diphenyl-1,4-di(3-phenylphenyDbutatnene.

1,4-dipheny1-1,4-dl(3-trifluoromethylphenyl) butatriene.

1 4-dipheny1-1 4-di- -ter hen 1 1- butatrlene. p p y y "The fihoteEdhduefi cr ramme meters (if r5515 The pregaiati ifafiiae atmuiaas'bf this ifiyention vention can be prepared by a number of well-known methods as described in the following references: Chapter 13, Cumulenes, by H. Fisher, The Chemistry of Alkenes, S. Patai, ed., lnterscience Publishers, London, New York, Sydney, 1,964, page 1025;

Cumulenes, Cadiot, Chodkiewicz, and Rauss Godisymmetrically substituted hexapentaenes may be obtained by potassium hydroxide-acetic acid *anhydride condens'ation'of l,l,diphe nylpropargylalcohol. The

24 hours. Such film forming resins as polyvinyl acetate, polyvinyl ethers, polystyrene, alkyd resins, phenylformaldehyde resins, styrene-butadiene copolymers, and polyamide resins may be employed as binders. The resin binder may comprise from 10 percent 75 percent by weight of the total weight of solids present in the photoconductive layer.

After the mixture is ball milled it is applied to a suitably conductive substrate by conventional coating techniques such as a meniscus coater, a wire wound rod or doctor blade at the rate of 0.5 grams to 2.0 grams per square foot, preferably 0.5 to l gram per square foot to produce a film thickness in the range of 0.1 mil to 5.0 mils in thickness, preferably in the range of 0.2

to 0.5 mil thickness. Evaporation of the solvent may be carried out by passing the coated web material through a forced air oven-type dryer.

It is generally known in the art dealing with the prep-. aration of photoconductive members, whether they are of the inorganic or organic type, that the photoresponse of such members may be improved through the addition of certain sensitizers or additives. in the case of inorganic photoconductive materials such as zinc oxide, these additives are in the form of dyes which increase the photoresponse by the mechanism of extending the spectral response of the photoconductive member. in the case of organic photoconductors involving donor-acceptor type materials or charge transfer type systems, the use of additives tends to extend the spectral response range or shift the spectral sensitivity into the visible portion of the spectrum and also tends to increase the sensitivity in a given spectral sensitivity range and thereby achieving a more efficient system.

It should be pointed out that the photoconductive materials of the instant invention exhibit the property of photoconductivity independent of the use of such additives or in fact independently of resin binders with which they may be combined. Such photoconductivity is determined by measuring the photocurrent of the materials coated on nesa glass surface cells or electrodes. The current which results, results when the charged nesa glass surface cell, which is coated with the specific chemical compound in a suitable solvent and evaporated to dryness, is illuminated with electromagnetic radiation represents the photocurrent. When referring to nesa glass surface cell measurement, the photoresponse is indicated in terms of the ratio of the photocurrent which results upon illumination of electromagnetic radiation to the dark current values.

Photoresponse of the compounds of the instant invention respond to radiation in the range of 375 to 600 millimicrons. While the compounds may be used to ad-. vantage without the use of sensitizers in this range of sensitivity to electromagnetic radiation, it is desirable to increase the degree of photoresponse and/or extend 2-Pheny1-4 8 the range of the sp e ctrafresponse. The organic photo conductors of the instant invention when measured on a nesa glass surface cell, exhibit a ratio of photocurrent to dark current in the range of 3010 1,000.

The cumulenes as a class of photoconductors exhibit an increase in photoresponse upon the addition of certain additives which are chemical sensitizers such as pitype acids such as disclosed in copending application Ser. No. 679,246 and Ser. No. 707,413, filed in the name of Evan S. Baltazzi, which inventions are assigned 7 to the same assignee as the instant invention.

The following list of pi-type sensitizers is representative of compounds of the dicyanomethylene fluorene type and the butenolides. 9-(dicyanomethylene)-3-nitrofluorene 9-(dicyanomethylene)-2,4-dinitrofluorene 9-(dicyanomethylene)-2,4,7-trinitrofluorene 9-(dicyanomethylene)-2,5-dinitrofluorene Q-(dicyanomethylene)2,6-dinitrofluorene 9-( dicyanomethylene )-2 ,7-dinitrofluorene 9-(dicyanomethylene)-2,4,5,7-tetranitrofluorene 9-( dicyanomethylene )-3 ,-dinitrofluorene 9-(dicyanomethylene)-2,4-dicyanofiuorene 9-(dicyanornethylene)-2,4,7-tricyanofluorene 9-(dicyanomethy1ene)-2,4,5,7-tetracyanofluorene 9-(dicyanomethylene)-2,4-ditrifluoromethylfluorene 9-(dicyanomethylene )-2,4,7-tritrifluoromethylfluorene 2'-Pheny1-4 oxazolone 2-Phenyl-4 (2,S-Dinitro-9-fluorenylidene )-5-oxazolone 2-Phenyl-4 (2,6-Dinitro-9-fluorenylidene)-5-oxazolone (2,4,7-Trinitro-9-fluorenylidene)-5- 2 -Phenyl-4 (2,7-Dinitro-9-fluorenylidene)-5-oxazolone 2-Phenyl-4 (2 ,4,5 ,7-Tetranitro-9-fluorenylide ne )-5 oxazolone 2-Pheny1-4 (3,6-Dinitro-9-fluorenylidene )-5 -oxazolone (2,4-Dicyan0-9-fluorenylidene)-5- oxazolone 2-Phenyl-4 (2,4,7-tricyano-9-fluorenylidene)-5- oxazolone 2-Phenyl-4 (2,4,5 ,7-Tetracyano-9-fl uorenylidene )-5- oxazolone 2-Phenyl-4 (2 ,4-di-trifluoromethyl-9-fluorenylidene 5-oxazolone 2-Phenyl-4 (2 ,4-Dichloro-9-fluorenylidene )-5 oxazolone 2-Phenyl-4 (2,4,7-Trichloro-9-fluoreny1idene )-5 oxa'zolone 2-Phenyl- 4 (2,4,5 ,7-Tetrachloro-9-fluorenylidene )-.5- oxazolone butenolide a-(2,5-Dinitro-9-iluorenylidene)-y-phenyl-A,ybutenolide a -(2,6-Dinitro-9-fluorenylidene-'y-phenyl-A ,ybutenolide a-(2,7-Dinitro-9-fluorenylidene)-'y-phenyl-A ;y butenolide a-(2,4,5,7-Tetranitro-9-fluorenylidene)-y-phenyl- A ,-y-butenolide a-( 3 ,6-Dinitr-9fluorenylidene )-y-phenyl-A,ybutenolide a-(2,4-Dicyano-9-fluorenylidene)-y-phenyl-A ,ybutenolide a-(2,4,7-Tricyano-9-fluorenylidene)-'y-phenyl-A ,'ybutenolide (Jr-(2,4,5,7-Tetracyano-9-fluorenylidene)-y-phenyl- A ,y-butenolide a-(2,4-Ditrifluoromethyl-9-fluorenylidene)-'y-phenyl- A ,-y-butenolide oz-(2,4-Dichloro-9-fluorenylidene)-'y-phenyl-A ,'ybutenolide a-(2,4,7-Trichloro-9-fluorenylidene)-'y-phenyl-A ,'ybutenolide a-(2,4,5,7-Tetrachloro-9-fluorenylidene)y-phenyl- A ,'y-butenolide In addition to the sensitizers referred to above, a large number of substances are disclosed in US. Pat. No. 3,037,861, issued to Helmut Hoegl, et a1, dated June 5, 1962, which discloses compounds from the class of mineral acids, organic sulfonic acids, organ' pho phonic acids, nitrophenols, acid anhydrides, metal halides of the metals and metaloids of the groups 1 B 2 through group 8 of the periodic system, boron halide compounds, organic substances containing CO- groups which are substantially monomeric, aldehydic compounds and ketonic materials.

The mechanism by which these additives enhance or increase the photoresponse is not fully understood.

Reference to increase in photoresponse of the photo conductive materials when applied in a uniform film to a paper substrate may be defined in terms of the rate of voltage drop dv/dt as a function of voltage. It is this measured rate of voltage drop, which when compared to photoconductive members without sensitizers, is increased over the same range of electromagnetic radiation which can vary from 360 millimicrons to 700 millimicrons.

The photosensitivity of the members-of the instant invention may be defined in terms of a conventional zinc oxide resin binder photoconductive member. The photosensitivity of the latter for the purpose of this invention has generally been assigned the arbitrary numerical rating of 150 units representing the standard or normal photoresponse when such exposure is accomplished using a tungsten-type filament source.

The sensitivity of the members of this invention which did not include the pi-type acids receivt d a rating of 1.0 relative to the standard zinc oxide member.

The photoelectrostatic members to which had been added thepi-type acids and which were exposed to a tungsten filament type lamp received a photosensitivity rating in the range of 80 to 210 units on this scale of comparison. In all cases the developed images which are obtained using the instant photoconductive members are of high contrast and good image density.

The amount of sensitizer employed may range from 0.1 to 5.0 moles per hundred moles of organic photoconductor. The preferred amount of sensitizer is between 0.5 to 1.5 moles per hundred moles of organic photoconductor. A typical sensitizer that may be used is 9-(dicyanomethylene)-2,4,7-trinitrofiuorene.

The process of making a reproduction utilizing the photoelectrostatic members of this invention involves applying a sensitizing electrostatic charge to the photoconductive layer in the range of 200 to 1,000 volts by means of a corona discharge electrode which is connected to a high potential source of from 4,000 to 7,000 volts. The materials of this invention may be charged either positively or negatively but exhibit a marked increase in sensitivity when charged positively. The charged layer upon receiving electrostatic charge in the dark, becomes sensitive to electromagnetic radi- I ation and is then exposed to a pattern of light and shadow by directing the radiation through a light transmitting original which is placed in contact over the photoconductive layer or by illuminating a graphic original with suitable electromagnetic radiation and then projecting the reflected pattern of light and shadow through a lens system onto the photoelectrostatic member.

Exposing the photoconductive layer to a pattern of light and shadow produces a corresponding electrostatic image with the charged area corresponding to the shadow portions and in the light struck areas the charge is dissipated. The charged pattern or image is rendered visible by the'application of a suitable toner which adheres to the image portionsPositively oriented toners are generally employed where the sensitizing charge is negative and reversal oriented toners are used for positively charged members, both systems producing a positive print from a positive original. The make-up of these toners is generally well known in the art and need not be further described here.

The material image is then fixed directly on the member or it may be transferred under controlled conditions to a receiving sheet, such as plain paper, and then fixed. The material image may be fixed by exposing the toner to a'source of heat which causes the material to coalesce and fuse to support. In the circumstance that the toners are pressure responsive, they can be fixed by the application of pressure such as passing the members between the set of pressure rollers.

The following examples are presented for illustrating the present invention without limiting the scope thereof.

EXAMPLE 1 A photoelectrostatic member was prepared by mixing 10- grams of bifiuorenylidene ethylene and 10 grams of styrenebutadienc copolymer sold by Goodyear Tire and Rubber Company under the tradename Pliolite SSD" in grams oftoluene. The mixture was ball milled at room temperature until complete blending was achieved requiring approximately 18 to 24 hours. The mix was then applied to a suitable'conductive support material such as aluminizedmylar 5 mil thickness using conventional coating equipment such as a meniscus coater ora wire wound rod. The solution was applied at a rate sufficient to produce a photoconducgrams per square foot. Evaporation of the toluene from the solution is accomplished by passing the coated web through forced hot air ovens maintained between 90 C. to 135 C.

The resulting member was charged positively and exposed to a pattern of light and shadow producing a latent electrostatic image thereon which was then developed by the application of a suitable electroscopic powder or toner. The photoresponse of the photoelectrostatic member was rated about 1.0 since the electrophotographic member was not sensitized.

1 claim:

1. An electrostatic imaging process for making reproductions of a graphic original on a photoelectrostatic member comprising the steps of applying a blanket of electrostatic charge to the surface of said member, ex-

posing said charged surface to a pattern of light and shadow, producing a latent electrostatic image thereon, and developing said latent electrostatic image by the application of toner powder thereon, said photoelectrostatic member comprising a conductive base support having a photoconductive layer applied thereon comprising an organic photoconductive compound dispersed in a resin binder, said photoconductive compound having one of the following formulas:

where x is alkyl, halogen, hydrogen or nitro, n is an integer from 1 through 6; Q1 and Q are selected from the group consisting of:

indene, or fluorene;

R is selected from the group consisting of lower alkyl, aryl or hydrogen; R and R can be aryl, substituted aryl or thienyl; and wherein O and Q or R, and R can be the same or different.

2. The process as claimed in claim 1 in which said photoelectrostatic member contains a pi-type sensitizer.

3. The process as claimed in claim 1 in which said photoelectrostatic member contains a sensitizer selected from the group consisting of dicyanomethylene fluorenes, phenyl fluorenylidene o tazolones and yphenyl-ABybutenolides.

4. The process as aairned in claim 1in which said sensitizer is present in the amount of from about 0.1 to about 5.0 mole percent, based on said organic photoconductive compound.

SIT he process as claimed in claim 1 in which said sensitizer is from about 0.25 to about 2.5 mole percent, based on said organic pho toconductive compound, of 9-dicyanomethylene)-2, 4, 7-trinitrofluorene.

6. The process as claimed in claim 1 in which said sensitizer is from about 0.5 to about 5.0 mole percent, based on said organic photoconductive compound, of 2-phenyl. 4 (2, 4, 5, 7 tetranitro 9 UNITED STATES PATENT OFFICE g 1 f 2 O QERTIFICATE OF CORRECTIGN Patent No. 3,841,871 Dated October 15, 1974 Inventor) Robert G. Blanchette It is certified that error appears in the above-identified patent Q and that said Letters Patent are hereby corrected as shown below:

ABSTRACT: Insert the following formula after the sentence "The cumulene compounds useful in the instant invention have of the following general formulas:"

Col, 4, line 1, change "Tetra-(m-bromophenyl hexapentaene" to I Tetra- (m-bromophenyl) hexapentaene Col. 5, Formula 21, This formula should read as follows: Q F C CF c c c c C01. 9, line 4, should read as follows: L- (2,4,7-Trinitro-9-fluorenylidene)- Y-phenyl- A ,Y-

Q Col. 9, line 8, should read as follows: a(2,6-Dinitro-9-fluorenylidene)- Y-phenyl- A Y- UNITED STATES PATENT OFFICE g 2 of 2 @ERTIFICATE OF CORRECTION Patent No. 3,841,871 Dated October 1974 Inventorflfi) Robert G. Blanchette It is certified that error appears in the above-identified patent Q and that: said Letters Patent are hereby corrected as shown below:

Col. 11, lines 28 35, delete the formulas in brackets.

Col. 11, lines 36 4 L, This formula should read as follows: 9 R

Col. 12, line 14, change "can be" to are selected from the group consisting Col. 12, line 34, should read as follows: 9- (dicyanomethylene)-2,4,7- 5 trinitrofluorene Col, 12, line 37, change "1" to 2 v Signed and Sealed this eighteenth D3) 0f May 1976 [SEAL] Arrest:

RUTH C. M K SON 'C. MARSHALL DANN v 11 (mnmissium'r uflau'nrs and Trademarks 

1. AN ELECTROSTATIC IMAGING PROCESS FOR MAKING REPRODUCTIONS OF A GRAPHIC ORIGINAL ON A PHOTOELECTROSTATIC MEMBER COCOMPRISING THE STEPS OF APPLYING A BLANDET OF ELECTROSTATIC CHARGE TO THE SURFACE OF SAID MEMBER, EXPOSING DAID CHARGED SURFACE TO A PATTERN OF LIGHT AND SHADOW, PRODUCING A LATENT ELECTROSTATIC IMAGE THEREON, AND DEVELOPING SAID LATENT ELECTROSTATIC IMAGE BY THE APPLICATION OF TONER POWDER THEREON, SAID PHOTOELECTROSATIC MEMBER COMPRISING A CONDUCTIVE BASE SUPPORT HAVING A PHOTOCONDUCTIVE LAYER APPLIED THEREON COMPRISING AN ORGANIC PHOTOCONDUCTIVE COMPOUND DISPERSED IN A RESIN BINDER, SAID PHOTOCONDUCTIVE COMPOUND HAVING ONE OF THE FOLLOWING FORMULAS:
 2. The process as claimed in claim 1 in which said photoelectrostatic member contains a pi-type sensitizer.
 3. The process as claimed in claim 1 in which said photoelectrostatic member contains a sensitizer selected from the group consisting of dicyanomethylene fluorenes, phenyl fluorenylidene oxazolones and gamma - phenyl- Delta Beta gamma - butenolides.
 4. The process as claimed in claim 1 in which said sensitizer is present in the amount of from about 0.1 to about 5.0 mole percent, based on said organic photoconductive compound.
 5. The process as claimed in claim 1 in which said sensitizer is from about 0.25 to about 2.5 mole percent, based on said organic photoconductive compound, of 9-dicyanomethylene)-2, 4, 7-trinitrofluorene.
 6. The process as claimed in claim 1 in which said sensitizer is from about 0.5 to about 5.0 mole percent, based on said organic photoconductive compound, of 2-phenyl - 4 - (2, 4, 5, 7 -tetranitro - 9 - fluorenylidene) -5- oxazolone. 